The present invention relates to a semiconductor integrated circuit for dual-band transmission/reception, in which a low noise amplifier is integrated, in a mobile terminal set for dual-band wireless communications, mainly applied to a wireless communication system for operating in two frequency bands, including a high frequency band and a low frequency band.
FIG. 4 shows an example of the construction of a terminal device to which a conventional semiconductor integrated circuit for dual-band transmission/reception (hereinbelow referred to as a “transmission/reception IC”) is applied. This is applied to a mobile terminal of a wireless communication system for operating in two different frequency bands. A transmission/reception IC 401 has a receiving mixer 403a for the high frequency band and a receiving mixer 403b for the low frequency band, applied to the dual-band wireless communication system, a next-stage mixer 404, a variable gain amplifier 405, a demodulator 406, a modulator 408, an offset PLL 409, and a divider 407. A local oscillation signal necessary for frequency conversion is supplied from a synthesizer 410 and external RF-VCO (Voltage Controlled Oscillator) for the high frequency band 413a, RF-VCO for the low frequency band 413b, internal IF-VCO 412 and the internal divider 407. A band pass filter 411 connected to the transmission/reception IC removes out-band spurs. An amplifier 402a for the high frequency band and an amplifier 402b for the low frequency band are external devices of the IC. In the transmission part, VCO for the high frequency band 414a and VCO for the low frequency band 414b are external. The local oscillation signal from the VCO is inputted to offset PLL 409 and the frequency of the modulated signal is converted to the transmission frequency. The high power amplifier for the high frequency band 415a and the high power amplifier for the low frequency band 415b amplify the transmission signal and the band pass filter 416 removes outband spurs. So far, it has been difficult to IC-incorporate the low noise amplifier due to shortage of gain in the high frequency band and noise characteristic by fT limitation of the transistor operation and the capacitance of the transistor substrate. However, the above problems have been overcome by recent improvements in fine processing, and so a low noise amplifier can be incorporated.
An example of a low noise amplifier applied to a dual-band transmission/reception IC is disclosed in “Dual-band High-Linearity Variable-Gain Low-Noise Amplifiers for Wireless Applications” by Keng Leong Fong, ISSCC 1999, pp. 224-225, p. 463. This construction, in which two low noise amplifiers for the dual-band transmission/reception IC are integrated as one chip and are sealed in a TSSOP20 pin package, does not include the entire transmission/reception system. Note that correspondence between the signal lines, the ground line and the like and the pads is unknown. Further, an example of a transmission/reception IC including a low noise amplifier is disclosed in “A Single-Chip CMOS Transceiver for DCS1800 Wireless Communications” by Michiel Steyaert et al., ISSCC 1998, pp. 48-49, p. 411. This construction, in which a transmission/reception circuit is integrated as one chip, is not applied to dual-band communications. Correspondence between the signal lines, the ground line and the like and the pads is unknown. Further, the package used there is unknown.